1. Field of the Invention
The present invention is related to a current sensor capable of detecting a change of a current flowing through a conductor with high precision, and a method of manufacturing such a current sensor.
2. Description of the Related Art
Generally, for an accurate measurement of a control current flowing through a circuit of a control device, there is used a method where a resistance is connected in series to a circuit so as to measure a voltage drop of the resistance. However, in this case, a load other than a lord of the control system is added, and thus the control system may be adversely influenced in some way. For this reason, there is used a method where a gradient of a current magnetic field generated by the control current is detected, and thereby the control current is indirectly measured. Specifically, the control current is supplied to a curved conductor having a U shape, and a change of the current magnetic field generated in the periphery of the curved conductor is detected by a hall element (for example, refer to Japanese Examined Patent publication No. Hei-7-123090).
However, in such a current sensor, miniaturization is difficult. Also an issue has been pointed out that the detection sensitivity with respect to the change of the magnetic field is insufficient in terms of a linearity and a high frequency response. Thus, a current sensor has been proposed where, instead of the hall element, a giant magnetoresistive element (hereinafter, referred to as a GMR element) exhibiting a giant magnetoresistive effect is arranged in the current magnetic field by the control current so as to detect the gradient of the current magnetic field. In the current sensor using such a GMR element, the detection sensitivity and the response characteristics are improved, and stable detection characteristics may be obtained, even if there is a temperature variation.